Overclocking:
We'll focus on the Ti4600 example for now. Click the "Clock Frequencies" tab to bring it to the foreground. This is what it looks like, and it's where everything from now on will happen:

Some details, like the numbers shown and the available range of values, will vary depending on the video card you are using. The "Core Clock Frequency" is the speed at which the Graphics Processor runs, be it a GeForce4, TNT2U chip etc. The "Memory Clock Frequency" is obviously the speed at which your memory runs - for DDR cards, it will display the DDR speed not the base MHz.

The first thing you need to to do is tick the "Allow clock frequency adjustments" box and click "Apply". In some circumstances the system will prompt you to reboot at that point so it can detect the default core and memory speeds of your card. I notice this doesn't seem to happen with the latest DetonatorXP's, or maybe it's the cards I've been using. Anyway don't panic, just reboot and come back to this window.

In simple terms, you slide the slider to the speed you're hoping for and click the "Test New Settings" button. It's normal for the screen to flicker or go blank, show a progress indicator, then flicker again. If nothing horrible happens during the test (bluescreen, spontaneous reboot, video corruption etc) you can click "Apply" and test with 3DMark or your favourite game. Realistically, I've never seen the "Test New Settings" button produce an error, even when the card was so highly overclocked it was unusable in games. However, the drivers require you to test the settings before you can apply them. Whatever you do, DON"T click the "Apply these settings at startup" button until you're absolutely sure that your card is stable at those speeds.

The basic principle is to separately clock the memory and the core until you start experiencing errors, then go back a small step. It's useful to have 3DMark open in the background so you can run the first few tests and make sure your card is working ok. In my experience, modern video cards benefit most from memory overclocking. Clocking the core up isn't going to achieve much if it's already starved for data from the memory. So, test the memory until you reach its limit, then start testing the core. Of course, you can try it the other way around if you like, use benchmarks to see which gives you the best results.

Common signs you have overclocked too far:

• White-spotted "snow" in games
• Mouse cursor disappears, becomes a "box of static" or leaves trails
• Textures (walls etc) flash, scroll, are the wrong colours or look distorted in games
• In DOS mode, text flashes or the wrong characters appear
• The "wrong thing" or noise appearing, any other odd graphical behaviour in windows or games

Some tips for overclocking using CoolBits:

• Don't just drag the sliders over to some crazily-high number and hope for the best. Take it gradually, a few MHz at a time. A good idea is to read reviews of your video card and see what the reviewers got it up to. Take note of what they are using for cooling and take it into account if you're using less powerful methods. Start your overclocking BELOW what you think you should be getting, based on what you know about your card, and work your way slowly upwards.
• As with any overclock, there is variation between the cards, even two of the same brand and model. Factors like ambient temperature, airflow over the card and even the quality of your power supply and motherboard can all affect the speed you reach. So don't automatically expect to get the same as your mate, even if he has the same card as you.
• When you overclock a component, you almost always raise its temperature. The cores of modern graphics cards run pretty hot already, so you will probably want to consider some kind of aftermarket cooling if you're going to run the core overclocked a fair way for a long time, or you could be risking the longevity of your card. Airflow is important, too! Make sure you have good airflow through your case so the card cooling can do its job.
• Don't just overclock for the sake of overclocking. Use benchmarks and your favorite games to see if there's really a noticeable improvement from the overclock. Otherwise you're raising the temperature and possibly risking your card for no reason. It may be that some other part of your system is the bottleneck.

"Apply these settings at startup"
Some final notes about this tickbox. Once you have found a core and memory speed you're happy with and you have tested in your favourite games/benchmarks, you could tick this box and the video driver will automatically set the card to these speeds every time you boot into windows. If you set this up with a speed that is beyond your card's limits, or you find that you suddenly start getting video corruption when you boot, hold down the CTRL key as Windows boots to tell CoolBits not to apply the overclocked settings. If you're logging onto a network, hold CTRL down immediately after logging on. A box telling you all this pops up when you click "Apply" after ticking this box anyway, but it's a good thing to remember in case you set it nice and high in winter, then when summer rolls around you suddenly get video corruption due to the higher amvient temperatures..

I don't play that many games, so I tend to leave the card at default speed most of the time - so I don't tick that box. When I want to play, I can always ramp the speed up before going into the game. I can set the speed back afterwards, or next time I reboot it will be set back to defaults anyway.

Remember: You're pushing components beyond their specified limits. Most people are now aware that equipment failure from overclocking is rare, and with manufacturers advertising "Overclocking Friendly!" on many products these days it's becoming more acceptable. But the risk is still there, no matter how small, so bear that in mind. You may be voiding your warranty by overclocking or changing the cooling on your card. Remember: nobody is forcing you to overclock and you do it at your own risk!